Door check



R. S. HERON Jan. 19, 1960 DOOR CHECK 2 Sheets-Sheet 1 Filed March 14,1956 INVENTOR Arron s.

Roam;- 6! Hake/v 16-5 BY R. S. HERON DOOR CHECK Jan. 19, 1960 2 N w e 09 w N E w W e 1 5 m w 2 4 8 a R Q \WI. 0% v H E. I v Whlfiflw' QINLLLNIIT I .IIIIIIFJFIIJUM! United States Patent DOOR CHECK Robert S.Heron, Brooklyn, Ohio, assignor, by mesne assignments, to Lisle W.Menzimer, Rockford, Ill., trustee Application March 14, 1956, Serial No.571,547

Claims. on. 16-82) This invention relates to door checks, and moreparticularly to door checks of the kind which will hold a door indifferent desired positions.

There exists a definite need for a satisfactory door check of this kind,particularly for the rear doors of delivery trucks of the panel bodytype. In such. delivery trucks it is desirable that the door check becapable of holding a rear door at either a substantially 180 full openposition or at a substantially 90 partially open position. The hingearrangement and balance for such a rear door are usually such that whenthe door is on one side of the 90 position it will tend to fall shut,and when the door is at, or on the other side of the 90 position, itwill tend to fall toward the full open or 180 position.

It is desirable that the door be openable to the 180 position so as topermit the rear end of the truck to be moved up close to a loading dockor platform without interference from the door. On the other hand, whenthe truck is standing at a curb or in a roadside position and the reardoors are opened, one of those doors, usually the left-hand door, ifopened to its 180 position, will extend into the adjacent trafiic laneand will create a hazard. It is, therefore, necessary that the doorcheck be capable of holding the door at the 90 open position so that thedoor will not extend into the adjacent traffic lane.

The present invention, accordingly, has, as one of its objects, theprovision of a novel door check which will .hold a door in differentdesired open positions, and which is of a relatively simple andpractical form capable of being readily manufactured and installed.

Another object is to provide such a door check which will automaticallyassume an engaged condition for holding the door in an intermediate openposition, such as a 90 position, and in which the engaged condition isreleasable for movement of the door to another, predetermined openposition or to its closed position.

Still another object is to provide a novel multiple doorposition doorcheck comprising an extensible articulated linkage which includes a pairof pivoted link members having their adjacent end portions in acoextending relation and carrying cooperating elements for establishingthe different door-holding settings, and in'which confining meansassociated with the link members confines the same substantially totheir coextending relation during the extension and contraction of thelinkage throughout the full range of door movements, the cooperatingelements being engageable and releasable by a limited relative movementbetween the link members in a direction transversely of the linkage. 7

Additionally, this invention provides such a multipleposition door checkin which means effective on at least one of the link members, preferablya friction means incorporated in one of the pivots tends to produce arelative movement between the link members transversely of the linkagefor causing engagement of the cooperating elements, in response torelative longitudinal movement between the'link members. i

Other objects and advantages of the invention will be Patented Jan. 19,1960 apparent in the following detailed description and in theaccompanying sheets of drawings forming a part of this specification,and in which:

Fig. 1 is a partial rear end elevation of a vehicle having swingabledoors equipped with door checks embodying the present invention;

Fig. 2 is a partial transverse horizontal section on a somewhat largerscale taken through the vehicle, as indicated by section line 22 of Fig.1 and showing the closed position of the left-hand door and thecorresponding collapsed condition of its associated door check;

Fig. 3 is a partial transverse horizontal section similar to Fig. 2 butshowing the door in its full-open position and the correspondingextended condition of its associated door check;

Fig. 4 is a partial vertical longitudinal section taken .through thedoor check as indicated by section line 4-4 of Fig. 3;

Fig. 5 is a partial vertical section on a somewhat larger scale andtaken through one of the pivotal connections of the door check, asindicated by section line 5-5 of Figs. 1 and 2;

Fig. 6 is a transverse vertical section taken on line 66 of Fig. 2; and

Fig. 7 is an end elevation of the door check when viewed as indicated bythe directional line 7-7 of Fig. 2.

By way of example, the drawings show the novel door check of the presentinvention applied to a delivery truck 10 of the panel body type having adoorway 11 in the rear end thereof and a pair of rear doors 12 and 13for closing such doorway. Door checks 14 and 15 of the novelconstruction provided by this invention are applied to the doors 12 and13 for holding the same in the desired full open, or partially open,positions in the manner to be explained hereinafter. The door checks 14and 15 are identical in construction, with the exception that they arefor right-hand and left-hand installation to suit the righthand andleft-hand doors 12 and 13 to which they are applied.

The doorway 11 of the truck 10 is defined by body portions constitutingthe door frame structure which includes upright side edge or pillarportions 16 and 17 and a transverse top portion or lintel 18. The doors12 and 13 are swingably mounted on the upright doorframe portions 16 and17 by pairs of suitable hinges 19 which are at-.

tached to these doorframe portions and to the adjacent upright edgeportions 20 and 21 of the doors. When the doors are in their closedposition, as shown in Fig. 1, their free edges 22 and 23 are in ameeting or engaged relation in or adjacent a common parting plane, andin this instance, the edge portion of the left-hand door 13 is providedwith a stop flange 25 with which the edge portion of the right-hand door12 has an abutting engagement in an overlapping relation thereto, asshown in Fig. 2.

The right-hand door 12 is here shown as provided with a suitable handle26 for swinging the same and, if desired, a similar handle can beprovided on the door 13. The doors 12 and 13 also include an upper edgewall 28 which is located adjacent to but below the transverse doorframeportion 18 when the doors are in their closed position.

For a more detailed description of the invention, reference need be madeonly to the left-hand door 13 andto the door check 15 associatedtherewith. As shown in Fig. 3, the door 13 is swingable from a closedposition 13* to intermediate and full-open positions 13 and 13. Theintermediate position 13* is a substantially position and the position13 is a substantially open posltion. i

The location of the hinges 19 is such that if the door 13 is in its 90position 13 and is then released, itwill tend to fall open toward its180 position 13, and if the thereagainst by the connecting screws 42.

door is somewhat to the right of the 90 position 13 when it is released,it will tend to fall shut. As will be explained more fully hereinafter,the door check 15 has an engaged condition providing an intermediatedoorholding length for holding the door 13 in the 90 position 13 andalso has a second engaged condition, which in this case is its fullyextended length, for holding the door in the 180 position 13.

The door check 15 is in the form of an extensible articulated linkagewhich comprises, in general, a pair of attaching members 29 and 33 forconnecting the opposite ends of the linkage with the door and doorframestructures respectively, and a linkage unit 31 extending between theattaching members and comprising a pair of link members 32 and 33 havingtheir adjacent ends in an overlapping or telescoping relation. The doorcheck 15 also comprises cooperating guideway and guide follower elementscarried by the link members, the guideway being here shown in the formof a longitudinal slot 34 in the link member 32 and the follower beinghere shown as a pin 35 carried by the link member 33 and movable alongsuch slot. As shown in Figs. 2 and 3 the slot 34 extends along the linkmember 32 for a major portion of the length of the latter.

The attaching member 29 can be of any appropriate form and is here shownas comprising a substantially flat plate bracket adapted to be securedto the top edge wall '28 of the door 13 by the connecting screws 36. Thebracket 29 carries a headed pivot member 38 by which the outer end 39 ofthe link member 32 is pivotally attached to this bracket.

The attaching member can also be a bracket made of sheet metal or platematerial and is here shown as being of a substantially L-shaped formhaving substantially right-angularly disposed flat upright andhorizontal legs 40 and 41. The bracket 30 can be mounted on thedoorframe member 18 with the flat upright leg 40 secured The horizontalleg 41 carries a pivot pin 43 by which the outer end 44 of the linkmember 33 is pivotally connected with this bracket.

The link member 32 can be a substantially straight bar of an appropriatelength and is here shown as being a sheet metal member of achannel-shaped crosssection having a substantially fiat longitudinal webportion 47 and substantially parallel longitudinal edge flanges 48 and49. The slot 34 extends along the link member 32 for a substantialportion of its length and is suitably formed in the web portion 47 ofthis member.

The slot 34 has longitudinally extending side edges 50 and 51 alongopposite sides thereof and one of those side edges, in this instance theside edge 51, has a laterally offset portion forming an abutmentshoulder or stop 52. The stop 52 is engageable by the follower pin forholding the door 13 in its intermediate or 90 position 13 as explainedhereinafter, and can be located at any appropriate point along the sideedge 51 of the slot 34, depending upon the position in which the door isdesired to be held. The stop 52 is here shown as being located adjacentthe midpoint of this side edge of the slot. Adjacent the stop 52, theslot 34 has a relatively wide tapered portion 54, such that the abutmentshoulder forming this stop faces toward the pivot 38 and is engageableby the pin 35 when the latter is moving along the slot in a directionaway from the pivot 38.

The link member 32 is provided with a second stop 55 which is engageableby the pin 35 for holding the door 13 in its full open or 180 position13. This second stop is here shown as being formed by the end of thestantiallyparallel relation to the web portion 47 of the link member 32.The link member 33 has a longitudinal flange 58 thereon, which is hereshown as being an edge flange formed on the end portion 59 of this linkmember which is overlapped by the adjacent end portion of the linkmember 32. As shown in the drawings, the pin 35 is mounted on the linkmember 31 so as to be spaced from the edge flange 58 thereof a distancesuch that this pin with be located directly opposite a,nd for movementinto, the open end of the narrow portion of the slot 34 when the flange58 is in engagement with the flange 49 of the link member 32.

The link members 32 and 33 are preferably disposed with the flangedsides thereof facing each other. The flanged end portion 59 of the linkmember 33 is wider than the link member 32 so as to extend across andbeyond the edge flanges 48 and 49 of the latter, as shown in Fig. 2. Thelink members 32 and 33 extend in a substantially longitudinally alignedrelation with one of the edge flanges of the link member 32, in thisinstance the edge flange 49, lying adjacent to and slidable along theflange 58 of the link member 33.

The guide follower pin 35 is mounted in a fixed relation on the wide endportion 59 of the link member 33 substantially on the longitudinalcenter line thereof and can be in the form of a pin whose stem portion60 is disposed in the slot 34 and whose reduced end 61 is secured inshouldered engagement with the web 57 by the riveted portion 62. The pin35 is provided with a disk-like head 63 and with a disk-shaped washer 64disposed on the stem 60 adjacent the head and spanning the slot 34. Thepin 35 thus serves as a connecting means for the overlapping portions ofthe link members 32 and 33 as well as a guide follower movable along theslot 34.

The proportions and dimensions of the link members 32 and 33 and thelocations of the brackets 29 and 30, are such that when the stem 60 ofthe follower pin 35 is engaged by the stop 52 of the link member 32, asshown in broken lines in Fig. 3, the door 13 will be retained in itspartially open position 13 by reason of the fact that the stop 52 isbeing pulled against the pin 35 by the weight of the door and thetendency of the latter to fall open. When the door 13 is swung to itsfull open position 13, the stop 55 formed by the end of the slot 34 willengage the stem 60 of the follower pin 35, as shown in Fig. 3 and thedoor will thereupon be held against further opening movement and theopening tendency of the door will maintain the stop 55 in engagementwith the pin 35.

When the door 13 is in its closed position 13, the linkage unit 31 is ina relatively collapsed condition in which the link members 32 and 33 arecoextending for a greater portion of their length, as shown in Fig. 2 ofthe draw ings. At this time the follower pin 35 is located in the endportion of the slot 34 which extends toward the pivot 38. As the door 13is swung open, the link member 32 moves with the door by reason of apulling force being applied to this link member through the pivot 38such that this link member is withdrawn from, or extended relative to,the link member 33. During this relative extending movement of the linkmember 32, the follower pin 35 moves along the slot 34 into engagementwith the stop 52 to establish the above-explained intermediate or doorposition 13 The relatively wide portion 54 of the slot 34 permits arelative movement between the link members 32 and 33 transversely of thelinkage for disengagement of the follower pin 35 from the stop 52. Thisrelative transverse movement between the link members 32 and 33 can beproduced by a manual force applied to oneor both of these link members,such as a manual force applied to the linkage with the thumb and fingersof the same hand engaging opposite sides of the linkage and squeezingthe link members toward each other, to thereby displace the follower pin35 from the stop 52 and toward the straight side edge 50 of the slot.When the follower pin 35 has been thus disengaged from the stop 52, itis free to move along the slot 34 toward the end stop 55 thereof. Thisfreedom of movement of the follower pin 35 permits further extension ofthe link member 32. relative to the link member 33 during which the door13 is being swung from the 90 position 13 to the full-open or 180position 13.

When the follower pin 35 is in engagement with the stop 52, the edgeflange 49 of the link member 32. and the flange 58 of the link member 33are in a relatively spaced-apart relation, as shown in Fig. 3, such thatthe above-described relative transverse movement between the linkmembers can readily take place upon the application of the manualsqueezing force to the linkage.

It is desirable that the pin 35 move into the wide slot portion 54during each opening movement of the door 13 so as to automaticallyengage the stop 52 when the door arrives at its 90 open position 13*.For this purpose the door check 15 is provided with means for producinga drag effect on one of the link members, in this instance the linkmember 33. This drag effect is produced, in accordance with the presentinvention, by incorporating frictional resistance in the pivot 43 in amanner which will now be described.

The pivot 43 can be in the form of a pin 66 having a reduced stemportion 67 riveted to the plate portion 41 of the bracket 30 and alsohaving a stem portion 68 extending through an opening 69 of the linkmember 33. A disk-shaped washer 70 of a bowed form is disposed aroundthe stem portion 68 and is confined by the head 71 of the latter so asto apply a clamping pressure against the link member 33 for pressing thesame in a face-toface engagement with the plate portion 41 of thebracket 30. The washer 70 is preferably a spring steel washer, which ismaintained under a loaded condition bythe assembled relation of thepivot member 43 with the bracket 30.

By reason of the frictional drag produced by the action of the washer70, the tendency of the link member 33 will be to resist swingingthereof in a counterclockwise direction, as seen in Figs. 2 and 3, bythe link member 32 such that during the opening movement of the door 13,the follower pin 35 will hug the side edge 51 of the slot 34 and willmove into the wide slot portion 54 and engage the stop 52, as explainedabove, during each opening movement of the door.

From the construction and operation of the door check 15 as abovedescribed it will be understood that the manual release of the pin 35from the stop 52 is only necessary when the door 13 is to be swung fromits 90' position to its full 180 position. When the door is being swungshut from either its 90 position or its 180 position, the pin 35 has afree movement along the slot 34 during which it hugs the straight sideedge 50 by reason of the frictional drag resisting clockwise swinging ofthe link member 32 on the pivot 43.

When the door 13 is being swung shut from its 90 position, the pin 35simply moves away from the stop 52 by moving along the slot 34 towardthe pivot 38. Likewise, when the door is being swung shut from its 180position, the pin 35 moves away from the Stop 55 and along the slot 34toward the pivot 38 and, since the pin at this time is moving in thesame direction as the stop 52 faces, the pin moves freely past the stopwithout engaging the same. The closing of the door from its fullopenposition thus takes place as a continuous and uninterrupted swingingmovement. I

Since the attaching bracket 29 is mounted on the door 13v at a pointadjacent the axis of the hingers 19 and the bracket 30 is mounted on thedoorframe 18 at a point spaced a substantial distance from the hingeaxis, it will be seen that as the door swings from its full-open 6position to its closed position, the link members 32 and 33 will alwaysremain in a substantially longitudinally aligned relation with theamount of overlap between the link members varying with the differentpositions assumed by the door. The maintaining of this substantiallyaligned relation of the link members gives the linkage unit 31 itsrigidity and ability to hold the door in the desired differentpositions. This aligned relation of the link members 32 and 33 resultsfrom the confining action of the cooperating flanges 49 and 58 of thesemembers, by which the relative movement between the link members in adirection transversely of the linkage is confined to merely the amountof movement therebetween needed to disengage the follower pin 35 fromthe stop 52.

From the accompanying drawings and the foregoing detailed description,it will accordingly be understood that this invention provides arelatively simple and practical form of door check which can be readilymanufactured and easily installed. It will now also be understood thatthis door check will effectively hold adoor in different desired openpositions and that the door-holding action for the intermediate positioncan be readily released by manual manipulation of the cooperating linkmembers.

Although the door check of the present invention has been illustratedand described herein to a somewhat detailed extent, it will beunderstood, of course, that the invention is not to be regarded as beinglimited correspondingly in scope since it is intended to include allchanges and modifications coming within the terms of th claims hereof.

Having thus described my invention, I claim:

1. A door check comprising an extensible articulated linkage including apair of link members extending in substantially the same direction withadjacent end portions of the link members in overlapping relation,attaching devices pivotally connected with the remote ends of said linkmembers and adapted for attachment to a door and its associated doorframe, means connecting said link members for relative movementtherebetween comprising guide means on one link member and extendingtherealong and guide follower means mounted in a fixed relation on theother link member, stop elements on said one link member and locatedadjacent said guide means and at spaced points along the latter, saidstop elements facing in the same direction along said guide means andbeing selectively engageable by said follower means for establishingdifferent door-positioning lengths for said linkage .for checkingmovement of said door in a given direction at different points of suchdoor movement, said guide and guide follower means having limitedrelative movement in a direction transversely of the linkage forengaging said follower means with and disengaging said follower meansfrom one of said stop elements, and means effective on said link membersfor confining the same to a substantially longitudinally alignedrelation during their relative longitudinal movements produced duringmovement of the door between its closed position and its full openposition.

2. A door check as defined in claim 1 in which said last named meansalso limits the extent of the transverse movement between said linkmembers and comprising a confining element extending along atleast oneof the link members and engaged by'a portion of the other link member.

3. A multiple door-position door check for use between: a support and adoor hinged thereto comprising, a first; attaching means adapted forconnection with said door, a second attaching means adapted forconnection with said support at a point spaced from the hinge axis, anin-- termediate linkage unit extending between and having: its endspivotally connected with said first and second attaching means, saidlinkage unit comprising a pair of link members one of which has aguideway extending longitudinally thereof, a plurality of stopsassociated with 1, said guideway including an end stop located at anend! of said guideway and an intermediate stop located at anintermediate point of the length'of said guideway and spaced from saidend stop said stopsfacing in the same direction longitudinally of saidguideway, and a follower fixedly mounted on and carried by the otherlink member and movable along said guideway and selectively engageablewith said stops for establishing different doorholding lengths for saiddoor check for checking movement of said door in a given direction atdifferent points of such door movement, said link members being in asubstantially longitudinally aligned and at least partially coextendingrelation and having a limited relative movement transversely of saidunit for the engagement and disengagement of said follower andintermediate stop, said guideway having a portion providing increasedwidth adjacent said intermediate stop and said follower being shiftablein the guideway portion of increased width during the transverserelative movement of said link members.

4. A door check comprising an extensible articulated linkage havingattaching members at the ends thereof for application to associated doorand doorframe members and including an intermediate linkage unitextending between and pivotally connected with said attaching members,said linkage unit comprising a pair of longitudinally disposed and atleast partially coextending link members one of which has a longitudinalslot and a stop adjacent one side edge of said slot and the other ofsaid link members having a projection fixed thereon and movable alongsaid slot, said projection being engageable with said stop forestablishing a given door-holding length for said linkage unit, meanseffective on one of said link members through the pivotal connectionthereof with its associated attaching member for causing said projectionto hug said one side edge during relative longitudinal movement in onedirection between said link members and to hug the other side edge ofsaid slot during relative longitudinal movement in the oppositedirection between said link members, and means for confining therelative longitudinal movement between said link memberssubstantially-to a relative movement in-the longitudinal direction ofand along said unit, said link members having a limited relativemovement transversely of said unit for engagement and disengagement ofsaid projection from said stop.

5. A multiple door-position door check for use between a support and adoor hinged thereto comprising, a first attaching means adapted forconnection with said door, a second attaching means adapted forconnection with said support at a point spaced from the hinge axis, an

intermediate linkage unit extending between said first and secondattaching means, first and second pivots pivotally connecting the endsof said linkage unit with said first and second attaching means, saidlinkage unit comprising a pair of link members one of which has aguideway extending longitudinally thereof, a plurality of stopsassociated with said guideway including an end stop located atan end ofsaid guideway and an intermediate stop spaced from said end stop, afollower carried by the other link member and movable along saidguideway and selectively engageable with said stops for establishingdifierent door-holding lengths for said linkage unit, said link membersbeing in a substantially longitudinally aligned' and at least partiallycoextending relation-and'having alimited relative movement transverselyof said unit for the engagement and disengagement of said follower andintermediate stop, and friction producing means associated with one ofsaid pivots to retard swinging of the associated link member on said onepivot for causing such transverse relative movement between said linkmembers in response to'relative longitudinal movement therebetween andin a direction for causing engagement between said follower and saidintermediate'stop;

6: A multiple door-position door check for use be tween a support and adoor hinged theretocomprisiri'gia' first attaching means adapted forconnection with said door and including a first pivot, a secondattaching means adapted for connection with said support at a pointspaced from the hinge axis and including a second pivot, an intermediatelinkage unit extending between and having its ends pivotally connectedwith said first and second attaching means by said first and secondpivots, said linkage unit comprising a pair of link members one of whichhas a longitudinal slot therein, a plurality of stops associated withsaid slot and including an end stop formed by an end of said slot and anintermediate stop located at an intermediate point of the length of saidslot and spaced from said end stop, said stops facing in the samedirection longitudinally of said slot, and a projection carried by theother link member and movable along said slot and selectively engageablewith said stops for establishing different door-holding lengths for saidlinkage unit, said link members being in a substantially longitudinallyaligned and at least partially co-extending relation during movement ofthe door between its closed and full open positions and having a limitedrelative movement transversely of said unit for the engagement anddisengagement of said projection and intermediate stop, one of saidpivots having a friction producing means therein tending to retardswinging of the associated linkmember on said one pivot to causeengagement between said projection and intermediate stop during relativelongi tudinal movement between said link members.

7. A door check as defined in claim 6 in which said friction producingmeans is in the pivot of said second attaching means and compirses aspring washer of bowed form embodied therein.

8. A door check as defined in claim 6 in which the link membercontaining said slot is of a channel form having longitudinal edgeflanges and the other link member has a longitudinal edge portionthereof lying adjacent and slidable along one of said edge flanges.

9. A door check comprising, a pair of link members at least one of whichhas a substantially flat longitudinal wall portion provided with a guideslot extending longitudinally therealong for a major portion of thelength of said one link member and the other of which has an end portionthereof overlapping said flat wall portion for at least a portion of thelength of the latter, said link members being disposed with the outerends thereof extending in generally opposite directions away from theoverlapped portions, attaching devices adapted for attachment to a pairof associated door and doorframe members, first and second pivotsconnecting the outer ends of said link members to said attachingdevices, said slot having an intermediate portion of increased widthextending along the slot for a portion of its length, a stop on said onelink member and located in said slot at an intermediate point of thelength of the slotand at one end of said portion of increased width, afollower fixed on said overlapping end portion of said other link memberand movable in said slot longitudinally of the latter during relativeendwise movements between said link members, confining portions on saidlink members and co-operably effective for maintaining the link membersin a longitudinally extending relation to each other during the fullextent of the permissible endwise relative movement between said linkmembers, said follower being confined in said slot during all portionsof the relative movement between said follower and slot and saidfollower being engageable with said stop for establishing apredetermined holding length for the door check, said link membershaving a limited relative movement in a direction transversely of saidslot while said follower is in said slot portion of increased width forcausing the follower to engage and disengage said stop, and frictionproducing means in one of said pivots for retarding swinging movement ofone of said link members relative to its associated attaching device tocause an automatic engageme'nt of s'aidfollower with said stop inresponse to 9 an extending endwise relative movement between said linkmembers.

10. A door check for checking door opening movement comprising, a pairof link members at least one of which has a substantially flatlongitudinal wall portion provided with a guide slot extendinglongitudinally there long for a major portion of the length of said onelink member and the other of which has an end portion thereofoverlapping said fiat wall portion for at least a portion of the lengthof the latter, said link members being dis posed with the outer endsthereof extending in generally opposite directions away from theoverlapped portions, attaching devices connected with said outer endsand adapted for attachment to a pair of associated door and doorframemembers, said slot having an intermediate portion of increased widthextending along the slot for a portion of its length, a stop on said onelink member and located in said slot at an intermediate point of thelength of the slot and at one end of said portion of increased width, afollower fixed on said overlapping end portion of said other link memberand movable in said slot longitudinally of the latter during relativeendwise movements between said link members, and co-operably eifectiveconfining portions on said link members for maintaining the link membersin a longitudinally extending relation to each other during the fullextent of the permissible endwise relative movement between said linkmembers, said follower being confined in said slot during all portionsof the relative movement between said follower and slot and saidfollower being engageable with said stop for establishing apredetermined holding length for checking the opening movement of saiddoor, said link members having a limited relative movement in adirection transversely of said slot while said follower is in said slotportion of increased width for causing the follower to engage anddisengage said stop, said one link member being a channel-shaped membercomprising a pair of spaced longitudinal side flanges connected by alongitudinal web portion which provides said fiat wall portion, saidoverlapping end portion of said other link member being a secondsubstantially fiat wall portion lying in a plane parallel to the planeof said web portion and being of greater transverse width than thetransverse spacing of said flanges.

References Cited in the file of this patent UNITED STATES PATENTS1,190,324 Rogers July 11, 1916 1,371,514 Nicol Mar. 15, 1921 1,898,280Winkelmann Feb. 21, 1933 1,912,105 Thompson May 30, 1933 2,021,357Goodwin Nov. 19, 1935 2,135,784 Bachor Nov. 8, 1938 2,220,876 CarterNov. 12, 1940 2,253,561 Harden Aug. 26, 1941

